/*
   * authencesn.c - AEAD wrapper for IPsec with extended sequence numbers,
   *                 derived from authenc.c
   *
   * Copyright (C) 2010 secunet Security Networks AG
   * Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>

   * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>

   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   */

  #include <crypto/internal/aead.h>

  #include <crypto/internal/hash.h>
  #include <crypto/internal/skcipher.h>
  #include <crypto/authenc.h>

  #include <crypto/null.h>

  #include <crypto/scatterwalk.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/rtnetlink.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  
  struct authenc_esn_instance_ctx {
  	struct crypto_ahash_spawn auth;
  	struct crypto_skcipher_spawn enc;
  };
  
  struct crypto_authenc_esn_ctx {
  	unsigned int reqoff;
  	struct crypto_ahash *auth;

  	struct crypto_skcipher *enc;
  	struct crypto_skcipher *null;

  };
  
  struct authenc_esn_request_ctx {

  	struct scatterlist src[2];
  	struct scatterlist dst[2];

  	char tail[];
  };
  
  static void authenc_esn_request_complete(struct aead_request *req, int err)
  {
  	if (err != -EINPROGRESS)
  		aead_request_complete(req, err);
  }

  static int crypto_authenc_esn_setauthsize(struct crypto_aead *authenc_esn,
  					  unsigned int authsize)
  {
  	if (authsize > 0 && authsize < 4)
  		return -EINVAL;
  
  	return 0;
  }

  static int crypto_authenc_esn_setkey(struct crypto_aead *authenc_esn, const u8 *key,
  				     unsigned int keylen)
  {

  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
  	struct crypto_ahash *auth = ctx->auth;

  	struct crypto_skcipher *enc = ctx->enc;

  	struct crypto_authenc_keys keys;

  	int err = -EINVAL;

  	if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)

  		goto badkey;

  
  	crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
  	crypto_ahash_set_flags(auth, crypto_aead_get_flags(authenc_esn) &
  				     CRYPTO_TFM_REQ_MASK);

  	err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen);

  	crypto_aead_set_flags(authenc_esn, crypto_ahash_get_flags(auth) &
  					   CRYPTO_TFM_RES_MASK);
  
  	if (err)
  		goto out;

  	crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
  	crypto_skcipher_set_flags(enc, crypto_aead_get_flags(authenc_esn) &

  					 CRYPTO_TFM_REQ_MASK);

  	err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
  	crypto_aead_set_flags(authenc_esn, crypto_skcipher_get_flags(enc) &

  					   CRYPTO_TFM_RES_MASK);
  
  out:

  	memzero_explicit(&keys, sizeof(keys));

  	return err;
  
  badkey:
  	crypto_aead_set_flags(authenc_esn, CRYPTO_TFM_RES_BAD_KEY_LEN);
  	goto out;
  }

  static int crypto_authenc_esn_genicv_tail(struct aead_request *req,
  					  unsigned int flags)

  {

  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
  	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);

  	struct crypto_ahash *auth = ctx->auth;
  	u8 *hash = PTR_ALIGN((u8 *)areq_ctx->tail,
  			     crypto_ahash_alignmask(auth) + 1);
  	unsigned int authsize = crypto_aead_authsize(authenc_esn);
  	unsigned int assoclen = req->assoclen;
  	unsigned int cryptlen = req->cryptlen;
  	struct scatterlist *dst = req->dst;
  	u32 tmp[2];

  	/* Move high-order bits of sequence number back. */
  	scatterwalk_map_and_copy(tmp, dst, 4, 4, 0);
  	scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 0);
  	scatterwalk_map_and_copy(tmp, dst, 0, 8, 1);

  	scatterwalk_map_and_copy(hash, dst, assoclen + cryptlen, authsize, 1);
  	return 0;

  }

  static void authenc_esn_geniv_ahash_done(struct crypto_async_request *areq,
  					 int err)
  {
  	struct aead_request *req = areq->data;

  	err = err ?: crypto_authenc_esn_genicv_tail(req, 0);

  	aead_request_complete(req, err);
  }

  static int crypto_authenc_esn_genicv(struct aead_request *req,
  				     unsigned int flags)

  {

  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);

  	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);

  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);

  	struct crypto_ahash *auth = ctx->auth;
  	u8 *hash = PTR_ALIGN((u8 *)areq_ctx->tail,
  			     crypto_ahash_alignmask(auth) + 1);

  	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);

  	unsigned int authsize = crypto_aead_authsize(authenc_esn);
  	unsigned int assoclen = req->assoclen;

  	unsigned int cryptlen = req->cryptlen;

  	struct scatterlist *dst = req->dst;
  	u32 tmp[2];

  	if (!authsize)
  		return 0;

  	/* Move high-order bits of sequence number to the end. */
  	scatterwalk_map_and_copy(tmp, dst, 0, 8, 0);
  	scatterwalk_map_and_copy(tmp, dst, 4, 4, 1);
  	scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 1);

  	sg_init_table(areq_ctx->dst, 2);
  	dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);

  	ahash_request_set_tfm(ahreq, auth);
  	ahash_request_set_crypt(ahreq, dst, hash, assoclen + cryptlen);
  	ahash_request_set_callback(ahreq, flags,
  				   authenc_esn_geniv_ahash_done, req);

  	return crypto_ahash_digest(ahreq) ?:
  	       crypto_authenc_esn_genicv_tail(req, aead_request_flags(req));

  }

  static void crypto_authenc_esn_encrypt_done(struct crypto_async_request *req,
  					    int err)

  {

  	struct aead_request *areq = req->data;

  	if (!err)
  		err = crypto_authenc_esn_genicv(areq, 0);

  	authenc_esn_request_complete(areq, err);

  }

  static int crypto_authenc_esn_copy(struct aead_request *req, unsigned int len)

  {
  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);

  	SKCIPHER_REQUEST_ON_STACK(skreq, ctx->null);

  	skcipher_request_set_tfm(skreq, ctx->null);
  	skcipher_request_set_callback(skreq, aead_request_flags(req),
  				      NULL, NULL);
  	skcipher_request_set_crypt(skreq, req->src, req->dst, len, NULL);
  
  	return crypto_skcipher_encrypt(skreq);

  }

  static int crypto_authenc_esn_encrypt(struct aead_request *req)

  {
  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
  	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);

  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);

  	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
  						  ctx->reqoff);
  	struct crypto_skcipher *enc = ctx->enc;

  	unsigned int assoclen = req->assoclen;

  	unsigned int cryptlen = req->cryptlen;

  	struct scatterlist *src, *dst;
  	int err;

  	sg_init_table(areq_ctx->src, 2);
  	src = scatterwalk_ffwd(areq_ctx->src, req->src, assoclen);
  	dst = src;

  	if (req->src != req->dst) {
  		err = crypto_authenc_esn_copy(req, assoclen);
  		if (err)
  			return err;

  		sg_init_table(areq_ctx->dst, 2);
  		dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, assoclen);

  	}

  	skcipher_request_set_tfm(skreq, enc);
  	skcipher_request_set_callback(skreq, aead_request_flags(req),
  				      crypto_authenc_esn_encrypt_done, req);
  	skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);

  	err = crypto_skcipher_encrypt(skreq);

  	if (err)
  		return err;

  	return crypto_authenc_esn_genicv(req, aead_request_flags(req));

  }

  static int crypto_authenc_esn_decrypt_tail(struct aead_request *req,
  					   unsigned int flags)

  {

  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
  	unsigned int authsize = crypto_aead_authsize(authenc_esn);
  	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);

  	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
  						  ctx->reqoff);

  	struct crypto_ahash *auth = ctx->auth;
  	u8 *ohash = PTR_ALIGN((u8 *)areq_ctx->tail,
  			      crypto_ahash_alignmask(auth) + 1);
  	unsigned int cryptlen = req->cryptlen - authsize;
  	unsigned int assoclen = req->assoclen;
  	struct scatterlist *dst = req->dst;
  	u8 *ihash = ohash + crypto_ahash_digestsize(auth);
  	u32 tmp[2];

  	if (!authsize)
  		goto decrypt;

  	/* Move high-order bits of sequence number back. */
  	scatterwalk_map_and_copy(tmp, dst, 4, 4, 0);
  	scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 0);
  	scatterwalk_map_and_copy(tmp, dst, 0, 8, 1);

  	if (crypto_memneq(ihash, ohash, authsize))
  		return -EBADMSG;

  decrypt:

  	sg_init_table(areq_ctx->dst, 2);
  	dst = scatterwalk_ffwd(areq_ctx->dst, dst, assoclen);

  	skcipher_request_set_tfm(skreq, ctx->enc);
  	skcipher_request_set_callback(skreq, flags,
  				      req->base.complete, req->base.data);
  	skcipher_request_set_crypt(skreq, dst, dst, cryptlen, req->iv);

  	return crypto_skcipher_decrypt(skreq);

  }

  static void authenc_esn_verify_ahash_done(struct crypto_async_request *areq,
  					  int err)

  {

  	struct aead_request *req = areq->data;

  	err = err ?: crypto_authenc_esn_decrypt_tail(req, 0);
  	aead_request_complete(req, err);

  }

  static int crypto_authenc_esn_decrypt(struct aead_request *req)

  {
  	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
  	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);

  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
  	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
  	unsigned int authsize = crypto_aead_authsize(authenc_esn);
  	struct crypto_ahash *auth = ctx->auth;
  	u8 *ohash = PTR_ALIGN((u8 *)areq_ctx->tail,
  			      crypto_ahash_alignmask(auth) + 1);
  	unsigned int assoclen = req->assoclen;
  	unsigned int cryptlen = req->cryptlen;
  	u8 *ihash = ohash + crypto_ahash_digestsize(auth);
  	struct scatterlist *dst = req->dst;
  	u32 tmp[2];
  	int err;

  	cryptlen -= authsize;

  	if (req->src != dst) {
  		err = crypto_authenc_esn_copy(req, assoclen + cryptlen);
  		if (err)
  			return err;
  	}

  	scatterwalk_map_and_copy(ihash, req->src, assoclen + cryptlen,
  				 authsize, 0);

  	if (!authsize)
  		goto tail;

  	/* Move high-order bits of sequence number to the end. */
  	scatterwalk_map_and_copy(tmp, dst, 0, 8, 0);
  	scatterwalk_map_and_copy(tmp, dst, 4, 4, 1);
  	scatterwalk_map_and_copy(tmp + 1, dst, assoclen + cryptlen, 4, 1);

  	sg_init_table(areq_ctx->dst, 2);
  	dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);

  	ahash_request_set_tfm(ahreq, auth);
  	ahash_request_set_crypt(ahreq, dst, ohash, assoclen + cryptlen);
  	ahash_request_set_callback(ahreq, aead_request_flags(req),
  				   authenc_esn_verify_ahash_done, req);

  	err = crypto_ahash_digest(ahreq);

  	if (err)
  		return err;

  tail:
  	return crypto_authenc_esn_decrypt_tail(req, aead_request_flags(req));

  }

  static int crypto_authenc_esn_init_tfm(struct crypto_aead *tfm)

  {

  	struct aead_instance *inst = aead_alg_instance(tfm);
  	struct authenc_esn_instance_ctx *ictx = aead_instance_ctx(inst);
  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);

  	struct crypto_ahash *auth;

  	struct crypto_skcipher *enc;
  	struct crypto_skcipher *null;

  	int err;
  
  	auth = crypto_spawn_ahash(&ictx->auth);
  	if (IS_ERR(auth))
  		return PTR_ERR(auth);

  	enc = crypto_spawn_skcipher(&ictx->enc);

  	err = PTR_ERR(enc);
  	if (IS_ERR(enc))
  		goto err_free_ahash;

  	null = crypto_get_default_null_skcipher2();

  	err = PTR_ERR(null);
  	if (IS_ERR(null))
  		goto err_free_skcipher;

  	ctx->auth = auth;
  	ctx->enc = enc;

  	ctx->null = null;

  	ctx->reqoff = ALIGN(2 * crypto_ahash_digestsize(auth),
  			    crypto_ahash_alignmask(auth) + 1);

  	crypto_aead_set_reqsize(
  		tfm,

  		sizeof(struct authenc_esn_request_ctx) +
  		ctx->reqoff +
  		max_t(unsigned int,

  		      crypto_ahash_reqsize(auth) +
  		      sizeof(struct ahash_request),
  		      sizeof(struct skcipher_request) +
  		      crypto_skcipher_reqsize(enc)));

  
  	return 0;

  err_free_skcipher:

  	crypto_free_skcipher(enc);

  err_free_ahash:
  	crypto_free_ahash(auth);
  	return err;
  }

  static void crypto_authenc_esn_exit_tfm(struct crypto_aead *tfm)

  {

  	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);

  
  	crypto_free_ahash(ctx->auth);

  	crypto_free_skcipher(ctx->enc);
  	crypto_put_default_null_skcipher2();

  }
  
  static void crypto_authenc_esn_free(struct aead_instance *inst)
  {
  	struct authenc_esn_instance_ctx *ctx = aead_instance_ctx(inst);
  
  	crypto_drop_skcipher(&ctx->enc);
  	crypto_drop_ahash(&ctx->auth);
  	kfree(inst);

  }

  static int crypto_authenc_esn_create(struct crypto_template *tmpl,
  				     struct rtattr **tb)

  {
  	struct crypto_attr_type *algt;

  	struct aead_instance *inst;

  	struct hash_alg_common *auth;
  	struct crypto_alg *auth_base;

  	struct skcipher_alg *enc;

  	struct authenc_esn_instance_ctx *ctx;
  	const char *enc_name;
  	int err;
  
  	algt = crypto_get_attr_type(tb);

  	if (IS_ERR(algt))

  		return PTR_ERR(algt);

  	if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & algt->mask)

  		return -EINVAL;

  
  	auth = ahash_attr_alg(tb[1], CRYPTO_ALG_TYPE_HASH,

  			      CRYPTO_ALG_TYPE_AHASH_MASK |
  			      crypto_requires_sync(algt->type, algt->mask));

  	if (IS_ERR(auth))

  		return PTR_ERR(auth);

  
  	auth_base = &auth->base;
  
  	enc_name = crypto_attr_alg_name(tb[2]);
  	err = PTR_ERR(enc_name);
  	if (IS_ERR(enc_name))
  		goto out_put_auth;
  
  	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
  	err = -ENOMEM;
  	if (!inst)
  		goto out_put_auth;

  	ctx = aead_instance_ctx(inst);

  	err = crypto_init_ahash_spawn(&ctx->auth, auth,
  				      aead_crypto_instance(inst));

  	if (err)
  		goto err_free_inst;

  	crypto_set_skcipher_spawn(&ctx->enc, aead_crypto_instance(inst));

  	err = crypto_grab_skcipher(&ctx->enc, enc_name, 0,
  				   crypto_requires_sync(algt->type,
  							algt->mask));

  	if (err)
  		goto err_drop_auth;

  	enc = crypto_spawn_skcipher_alg(&ctx->enc);

  
  	err = -ENAMETOOLONG;

  	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
  		     "authencesn(%s,%s)", auth_base->cra_name,

  		     enc->base.cra_name) >= CRYPTO_MAX_ALG_NAME)

  		goto err_drop_enc;

  	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,

  		     "authencesn(%s,%s)", auth_base->cra_driver_name,

  		     enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)

  		goto err_drop_enc;

  	inst->alg.base.cra_flags = (auth_base->cra_flags |
  				    enc->base.cra_flags) & CRYPTO_ALG_ASYNC;
  	inst->alg.base.cra_priority = enc->base.cra_priority * 10 +

  				      auth_base->cra_priority;

  	inst->alg.base.cra_blocksize = enc->base.cra_blocksize;

  	inst->alg.base.cra_alignmask = auth_base->cra_alignmask |

  				       enc->base.cra_alignmask;

  	inst->alg.base.cra_ctxsize = sizeof(struct crypto_authenc_esn_ctx);

  	inst->alg.ivsize = crypto_skcipher_alg_ivsize(enc);
  	inst->alg.chunksize = crypto_skcipher_alg_chunksize(enc);

  	inst->alg.maxauthsize = auth->digestsize;

  	inst->alg.init = crypto_authenc_esn_init_tfm;
  	inst->alg.exit = crypto_authenc_esn_exit_tfm;

  	inst->alg.setkey = crypto_authenc_esn_setkey;
  	inst->alg.setauthsize = crypto_authenc_esn_setauthsize;
  	inst->alg.encrypt = crypto_authenc_esn_encrypt;
  	inst->alg.decrypt = crypto_authenc_esn_decrypt;

  	inst->free = crypto_authenc_esn_free,

  	err = aead_register_instance(tmpl, inst);
  	if (err)
  		goto err_drop_enc;

  
  out:
  	crypto_mod_put(auth_base);

  	return err;

  
  err_drop_enc:
  	crypto_drop_skcipher(&ctx->enc);
  err_drop_auth:
  	crypto_drop_ahash(&ctx->auth);
  err_free_inst:
  	kfree(inst);
  out_put_auth:

  	goto out;
  }

  static struct crypto_template crypto_authenc_esn_tmpl = {
  	.name = "authencesn",

  	.create = crypto_authenc_esn_create,

  	.module = THIS_MODULE,
  };
  
  static int __init crypto_authenc_esn_module_init(void)
  {
  	return crypto_register_template(&crypto_authenc_esn_tmpl);
  }
  
  static void __exit crypto_authenc_esn_module_exit(void)
  {
  	crypto_unregister_template(&crypto_authenc_esn_tmpl);
  }
  
  module_init(crypto_authenc_esn_module_init);
  module_exit(crypto_authenc_esn_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
  MODULE_DESCRIPTION("AEAD wrapper for IPsec with extended sequence numbers");

  MODULE_ALIAS_CRYPTO("authencesn");